Engineered bio-inspired coating for passive flow control

Humberto Bocanegra Evans, Ali M. Hamed, Serdar Gorumlu, Ali Doosttalab, Burak Aksak, Leonardo P. Chamorro, Luciano Castillo

Research output: Contribution to journalArticlepeer-review


Flow separation and vortex shedding are some of the most common phenomena experienced by bluff bodies under relative motion with the surrounding medium. They often result in a recirculation bubble in regions with adverse pressure gradient, which typically reduces efficiency in vehicles and increases loading on structures. Here, the ability of an engineered coating to manipulate the large-scale recirculation region was tested in a separated flow at moderate momentum thickness Reynolds number, Re- = 1, 200. We show that the coating, composed of uniformly distributed cylindrical pillars with diverging tips, successfully reduces the size of, and shifts downstream, the separation bubble. Despite the so-called roughness parameter, k+ ≈1, falling within the hydrodynamic smooth regime, the coating is able to modulate the large-scale recirculating motion. Remarkably, this modulation does not induce noticeable changes in the near-wall turbulence levels. Supported with experimental data and theoretical arguments based on the averaged equations of motion, we suggest that the inherent mechanism responsible for the bubble modulation is essentially unsteady suction and blowing controlled by the increasing cross-section of the tips. The coating can be easily fabricated and installed and works under dry and wet conditions, increasing its potential impact on a diverse range of applications.

Original languageEnglish (US)
Pages (from-to)1210-1214
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number6
StatePublished - Feb 6 2018


  • Adverse pressure gradient
  • Bio-inspired surface
  • Engineered surface
  • Flow control
  • Flow separation

ASJC Scopus subject areas

  • General


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